180 BOTANY. the teeth tipped with longer spines than are found on the inter-dental margins; heads many, 1-1 J' in diameter, the subtending bracts spiny- margined and tipped; outer involucral scales strongly cihate-fringed ; inner ones less so, except at the tip, which has a smaU, oblong, ciliate, spine-tipped appendage 1-2" long and half as wide; flowers light yeUow.—Twin Lakes, Colorado (460). Centaueea* Ameeicana, Nutt—Erect, 4°, smooth; leaves sessile, entire, glabrous or nearly so, but with margins slightly ciliate; heads, including the long purple rays, 4' in diameter; outer scales of the involucre very short and tipped with a lanceolate, brown, pectinate-cihate appendage as long, or longer than the scales, the inner series becoming regularly longer and more scarious, the appendage remaining same size as in the outer series; pappus of rigid, simUar, roughish bristles.—Chiricahua, Southern Arizona (527). . PEEEZiAf Weighth, Gray (Pl. Wright 1, p. 127).—" Smoothish; the leafy herbaceous stem 2° high, from a perennial root; leaves thin, mem¬ branaceous, oblong-ovate, spinulose-denticulate, the larger doubly dentate, sessile and at base often auriculate; compound corymb polycephalous; heads 8-10-flowered, sub-fasciculate, involucre viscid sub-puberulent, scales hardly in 3 series, oblong and rather obtuse; achenia glandular, the soft white pappus of delicate bristles. Well distinguished by its membranaceous lea,ves and small heads " Not having the plant, I have quoted the original description.—Arizona. Peeezia nana. Gray (Pl. Fendl. p. 111).—2'-12' high, the single- headed leafy branches erect from a woolly, creeping root; leaves thickish, strongly reticulate, ovate or a little cuneate at base, sessile, very irregularly toothed, teeth spiny or mucronate-tipped from the produced nerves; heads * Cbntaurea, L.—Heads many-flowered; ray-flowers mostly large and sterile, sometimes wanting; involucre various, imbricated. Eeceptacle setose. Achenia compressed. Pappus occasionally wanting or nearly so, but usually composed of scabrous filiform bristles, iu one or more series, the inner often smaller and somewhat connivent.—T. & G. tPEREZiA, Lagasca.—"Head several-many-flowered; the flowers all perfect. Involucre turbinate or campanulate; its scales imbricated, lanceolate or oblong, mostly chartaceous. Eeceptacle fl.at and naked. Corolla with a slender tube and bilabiate limb; the outer lip much longer and 3-toothed; the inner 2-toolhed or 2-cleft. Anthers with long naked tails at base, and a lanceolate terminal appendage. Akenes elongated-oblong, terete or slightly angled, often obscurely narrowed at apes, commonly glandu¬ lar. Pappus of copious scabrous capillary brisf les.—Herbs; with alternate and mostly rigid leaves, and solitary or usually paniculate heads of purple or white flowers."—Gray, Fl. Cal. 1, p. '122.